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Fix points-to SCC collapsing bug

Message ID 20240527125807.D124B387088F@sourceware.org
State New
Headers show
Series Fix points-to SCC collapsing bug | expand

Commit Message

Richard Biener May 27, 2024, 12:57 p.m. UTC 
When points-to analysis finds SCCs it marks the wrong node as being
part of a found cycle.  It only wants to mark the node it collapses
to but marked the entry node found rather than the one it collapses
to.  This causes fallout in the patch for PR115236 but generally
weakens the points-to solution by collapsing too many nodes.  Note
that this fix might slow down points-to solving.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

	* tree-ssa-structalias.cc (scc_visit): Mark the node we
	collapse to as being in a component.
---
 gcc/tree-ssa-structalias.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/gcc/tree-ssa-structalias.cc b/gcc/tree-ssa-structalias.cc
index 3099658f100..53552b63532 100644
--- a/gcc/tree-ssa-structalias.cc
+++ b/gcc/tree-ssa-structalias.cc
@@ -1542,8 +1542,10 @@  scc_visit (constraint_graph_t graph, class scc_info *si, unsigned int n)
 		  graph->indirect_cycles[i - FIRST_REF_NODE] = lowest_node;
 		}
 	    }
+	  bitmap_set_bit (si->deleted, lowest_node);
 	}
-      bitmap_set_bit (si->deleted, n);
+      else
+	bitmap_set_bit (si->deleted, n);
     }
   else
     si->scc_stack.safe_push (n);